Return requirements: exchanges or refunds are only allowed if the kefir grains arrived defective (such as if the package arrived punctured, or similar). In cases like that I'll refund you, or send you another depending on the issue. No need to mail it back unless I ask you to. Just take some pictures of the problem, email me about it, and include them with all the details.
Return window notice: let me know of any problems within 2 days of you receiving the item. Note that returns are only allowed for physical damage like I said above. It does NOT include you trying to make kefir properly (so in cases like that just ask for help, and use the same email on the package / insert).
Return cost: $0